Chemical Constituents from Rheum ribes Shoots and its Insecticidal Activity Against Aedes aegypti

A phytochemical investigation of hexane extract of Rheum ribes L., Polygonaceae, shoots was analyzed by gas chromatography with flame ionization dection and mass specrometry and revealed seven components including methyl hexadecanoate (methyl palmitate) (2.4%), ( Z )-9-methyl octadecenoate (methyl oleate) (2.9%), ( Z , Z , Z )-9,12,15-methyl octadecatrienoate (methyl linolenate) (3.5%), 1-octadecanol (4.3%), ( Z , Z )-9,12-methyl octadecadienoate (methyl linoleate) (5.7%), heptacosane (13.5%), and hexadecanoic acid (palmitic acid) (67.7%). The hexane extract was bioassayed for larvicidal and adult topical activity against an insecticide susceptible strain of Aedes aegypti , the yellow fever mosquito. Results demonstrated a 90% mortality against adults at 5 μg/mosquito and first instar larvae at 1 μg/μl. The major compound hexadecanoic acid showed 20% mortality at 6.25 ppm against adults whereas the compound provided 100% mortality at the highest screening dose of 1000 ppm against 1st instar larvae. The mosquitocidal activity of the analyzed plant material may be related to a specific combination of compounds present in the hexane extract. Graphical abstract